Contents

Install OpenVPN

The first step toward a running OpenVPN installation is to install OpenVPN. On FreeBSD, we can do so from the ports tree:

cd /usr/ports/security/openvpn && make install clean

Once the installation is complete, we need to setup our directories for storing our SSL keys, CRL, etc. I keep all this information in /usr/local/etc/openvpn.

mkdir /usr/local/etc/openvpn

In order for OpenVPN to start, we need to add the following line to /etc/rc.conf:

openvpn_enable="YES"

Setup SSL Certificates/Keys

I think setting up SSL is the toughest part of OpenVPN for most people, including myself. I've written a script to help manage my network OpenSSL certificates. You can download this file here. Extract the tgz in your home directory (for now). You should see two files, ssl-admin.pl, and openssl.cnf.

Tuning ssl-admin.pl

You must edit the perl script to work correctly on your network. When initially downloaded, the script with exit, reminding you to setup all the variables at the top of the file. By default, the top of the file looks like this:

There are a couple points to note. First, make sure you comment out the die("... line. Failure to do so will result in the script failing to run. Second, the KEY_CRL_LOC is an optional variable, for use if you want to make your certificate revocation list available to the public. This script will not upload the CRL to your URI location. This must be manually done.

For OpenVPN purposes, I would not recommend making a key smaller than 1024. The KEY_DAYS variable determines how long your certificates are good for. Essentially, this is how often you'll have to reissue ssl certificates to your users. You can always revoke a certificate, so there's little worry about lost/stolen/fired/etc users.

Lastly, your KEY_DIR directory must already exist, or the script will error out. In our test installation here, we need to create this directory:

mkdir /usr/local/etc/openvpn/ssl

I keep my ssl-admin.pl script in /usr/local/etc/openvpn. This script will keep all of the files it needs to run in its own directory, which helps keep this my openvpn directory clean.

Executing ssl-admin.pl

We should now be ready to run ssl-admin.pl for the first time. Please note, you will need to have perl 5.8.8 or later installed for this script to run. At this time, there are no other dependencies. To run the script, simply use the following command:

KEY_DIR/ssl-admin.pl

Replace KEY_DIR with the directory where the ssl-admin.pl script resides. If you're CWD is that directory, use the following command:

./ssl-admin.pl

First Run

The first time (after you've set your variables), you're going to be prompted to either create a new CA root certificate, or point the script to your existing one. For the purpose of this document, we're going to create a new certificate.

For the certificate owner's name, I used vpn. Note, you cannot have spaces, capitol letters, or special characters.

ALWAYS protect your CA certificate with a password. Otherwise, why have a VPN if you're going to give keys to the world?

You'll note that most questions are answered automatically for you, based on the variables at the head of our script.

Once the CA certificate has been created (or pointed to), you should get a menu that appears as follows:

I'll cover the full operation of my script in another document, but you should be able to figure out most of the functions on your own. Please feel free to email me at ecrist@secure-computing.net with specific questions or bugs. Also, please, please, please, feel free to help me and add to/modify this script. Send me you updates!

OpenVPN Configuration

Now that we've got our SSL setup complete, we can move on to setting up the remainder of OpenVPN. To begin, we need a Diffie Hellman key. Create this with the following command:

openssl dhparam -out KEY_DIR/active/dh1024.pem 1024

Replace KEY_DIR with your OpenVPN directory.

Finally, we can create our OpenVPN configuration file. I will show you the file I use, and explain the entries as best I can:

daemon - This tells OpenVPN that we want to run a server. On client machines, you'll use client.
port 1194 - The tells OpenVPN to run on port 1194.
proto udp - Run with UDP protocol. I don't know why this is better than TCP, if it is.dev tun - What device to use. Use tun for routed OpenVPN.
ca/cert/key/dh - If you're using my ssl-admin.pl script, your keys/certficates will be in KEY_DIR/active/.
server - The IP address and subnet the virtual interface should have. Your clients will get addresses on this network.
push - We're pushing our LAN network route across to the VPN clients. Note, the 192.168/16 network is not advised, as most home networks run on this network, and routing will break for your client.
client-to-client - This is necessary for clients to reach other clients behind the OpenVPN gateway.
keepalive 10 120 -
duplicate-cn - Allow clients to connect more than once.
user/group - The user and group openvpn should run as.
persist-key/tun - Try to avoid accessing certain resources after perms have downgraded.
status - Keep a log of openvpn status.
log-append - Log file for messages, append rather than truncate.
verb 4' - Log file verbosity. 4 is 'reasonable.' Max of 9.crl-verify - IMPORTANT This tells openvpn to verify ssl certificates against our Certificate Revocation List.